Many commercial applications involve placing objects on target surfaces for later processing and/or use. Some applications involve placing objects, such as packages, product parts, or components, in trays, bowls, or other receptacles for transport along conveyor belts. For example, in some logistic applications, objects are placed on trays running along a conveyor belt for automated sorting. In some instances, an unexpected occupied receptacle can cause disruptions to the process, resulting in reduced efficiency. In some instances, the presence of an object can indicate a failure of an upstream process.